This invention relates to mineral ore pellets. More particularly, it relates to mineral ore pellets prepared from finely divided mineral ores.
Certain mineral ores are encountered in a finely divided state, either because they so occur naturally or because they are reduced to such a state for beneficiation. Typical of the latter ores are fluorspar (CaF.sub.2), olivine sand, taconite (a low grade iron ore), manganese and chrome ores, and mixtures thereof. The finely divided state of these ores may present difficulties, such as dusting or caking, in subsequent operations involving the ores.
Ores which are charged into metallurgical furnaces, such as taconite or fluorspar, present special difficulties if they are in a finely divided state, because they are often blown out through the furnace stack with the violent currents of gases present in such furnaces.
To overcome these difficulties, finely divided mineral ores are conventionally shaped into pellets, such as briquettes, balls, or various extruded forms. These various forms are intended to prevent dusting, crumbling, or caking of the ores and provide a free flowing, moisture resistant product which will resist being blown out of a blast furnace through the furnace stack. To insure that ore pellets have these qualities, yet are suitable for their intended purposes, it has been found that the pellets should be porous and uniformly hard throughout their structure. The pellets are preferably resistant to abrasion and impact so that fines are not formed during storage and handling, and, to allow outside storage, they are advantageously moisture resistant.
Heretofore, mineral ore pellets have been prepared by binding the ore particles with such materials as portland cement, bentonite clay, bentonite in combination with a soap, sodium silicate, organic resins, and related materials. Pellets prepared with such binders sometimes suffer from disadvantages. For instance, they may lack sufficient resistance to physical abrasion or impact or to moisture, or they may contain undesirable high concentrations of contaminating compounds, e.g. silica.